In power converters adapted for hybrid vehicles, electric vehicles, and the like, semiconductor-modules are widely used. Such semiconductor-modules, which implement controllers for energy saving, are provided with power semiconductor devices configured to control high current. Typical power semiconductor devices generate heat while controlling high current. The heat generated by power semiconductor devices increases as the power converters are miniaturized smaller and smaller, or outputs of the power converters increase higher and higher. Accordingly, semiconductor-modules including a plurality of power semiconductor devices have a serious cooling problem.
With the goal of improving the cooling efficiency of semiconductor-modules, liquid-cooled devices have been used. The liquid-cooled devices are developed with various manners such as a scheme of increasing the flow rate of the coolant to improve the cooling efficiency, a scheme of designing fins (cooling bodies) for radiation to have a shape that can provide a high heat transfer coefficient, and a scheme of employing fins made of a higher thermal conductivity material (Patent Literatures (PTLs) 1 to 8, for example).
However, when the flow rate of the coolant in the cooling device is increased or a complex fin shape providing high heat transfer rate is employed, the pressure loss of the coolant increases in the cooling device, thus increasing the load on a cooling pump that circulates the coolant. As for a cooling device that uses a plurality of heat sinks to cool a number of power semiconductor devices in particular, the pressure loss is predominantly increased by the channel configuration in which a plurality of channels are connected in series. Ideally, to decrease the pressure loss, the cooling device has a configuration that can provide a higher cooling efficiency at a low flow rate of the coolant. For example, it is only necessary to employ a fin material having a higher thermal conductivity. However, the employment of a fin material having a high thermal conductivity could increase the entire cost of the cooling device.
In order to decrease the pressure loss while keeping the cooling performance, in some conventionally proposed cooling devices, a coolant introduction channel for introducing a coolant and a coolant extraction channel for extracting the coolant are arranged in parallel to each other, and a plurality of heat sinks are arranged in an area between the coolant introduction and extraction channels so as to extend in a direction that the coolant flows, the direction being substantially orthogonal to the coolant introduction and extraction channels (see PTLs 9 to 13, for example).
Herein, in the case of PTL 13, in the coolant extraction channel extending toward a coolant outlet, a flow rate control plate is provided in parallel to a one side-surface of the heat sink so as to be spaced from the heat sink. The flow rate of the coolant flowing from the coolant introduction channel to the other side-surface of the heat sink can be thereby controlled. It is therefore possible to effectively cool semiconductor devices provided on the outer surface of the cooler, thus enabling stable operation of the semiconductor devices.